Note: Descriptions are shown in the official language in which they were submitted.
CA 02523737 2005-10-18
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FIELD OF THE INVENTION
This invention relates to a composition for use in making paper, pulp or
paperboard; and a process of making paper, pulp or paperboard employing the
composition, especially to add opacity to the paper, pulp or paperboard and a
paper, pulp or paperboard produced using the composition.
BACKGROUND OF THE INVENTION
In paper and paperboard manufacture, sheet formation is generally obtained on
wire webs in a wet end from pulp slurry and is followed by the gradual removal
of
moisture in a press section and drier section. A calender section follows the
drier
section with the purpose of obtaining a desired finish, for example,
smoothness,
thickness or gloss.
Despite the real advantages of using mechanical action to impart certain
characteristics to the sheet, these advantages are limited. Complementary
solutions
for improving even further certain paper or paperboard characteristics can be
applied internally in the wet end or externally with size-presses or waters
when
these are available. These solutions are related to the use of fillers and
functional
additives.
Fillers are generally white pigments that can be divided into two major
categories:
a) regular fillers having wide application and cost lower than that of
cellulosic
fiber, e.g. kaolin clay, ground calcium carbonate and precipitated calcium
carbonate;
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b) specialized fillers having usually lower volume applications and costs
sometimes comparable with or even higher than cellulosic fiber;
Some examples are: anatase titanium dioxide, ruble titanium dioxide,
composite pigments, e.g. clay and titanium dioxide, PSS (precipitated
synthetic
silica - silica oxides and precipitated silicate - aluminum silicate), talc
(industrial grade hydrated magnesium silicate), aluminum trihydrate, calcium
sulfate, natural or precipitated barium sulfate, zinc oxide, zinc sulfur -
surface
treatments only, Satin White (calcium sulfo-aluminate complex) - surface
treatments only, urea formaldehyde resin (organic pigment), plastic pigments
(empty or full spheres) - surface treatments only.
The advantages brought by fillers in paper or paperboard manufacture are
mostly
related to cost reductions, except with some of the specialized fillers,
especially
titanium dioxide. The process disadvantages are however important and concern
mostly wire, felt, doctor blade, refiners abrasion, machine deposits increase,
increased liming dust, breaks related to sheet strength decrease and filler
retention
difficulties requiring retention program solutions.
On the other hand, the functional advantages, with respect to final product
characteristics, brought by fillers are also important: optical properties,
i.e.
brightness and opacity, improvement, improved printability, better sheet
formation, increased smoothness and improved dimensional stability. The
functional disadvantages are mostly related to increased two sidedness,
reduced
rigidity, increased liming and decreased sheet strength.
Improving the paper or paperboard characteristics beyond the mechanical limits
of
a paper or paperboard machine often requires the use of fillers for their
functional
advantages and the use of functional additives for even better results.
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Examples of functional additives which can improve the sheet characteristics
are
dyes and optical brighteners, coating polymers, wet and dry strength resins,
sizing
agents, fluorocarbons, traditional organic opacifying agents and other
specialty
additives, while process additives that improve the production process include
biocides, deposit-control agents, felt conditioners and cleaners, defoamers,
and
effluent treatments.
Traditional organic opacifying agents are important functional additives used
to
improve the sheet characteristics obtained with mechanical means and with
filler
use. Resistance to water penetration, better printing characteristics,
increased
opacity brightness and whiteness, increased bulk and caliper, better
formation,
have been investigated and often obtained. Some process improvements related
to
reduced abrasion and cost reduction have also been noticed in some cases.
The following examples illustrate some of the traditional organic opacifiers:
U.S. Pat. Nos. 5,296,024 and 5,292,363 disclose a composition for enhancing
opaqueness in papermaking comprising the reaction product of a fatty acid and
a
diamine.
Different US patents related to US 5,296,024 indicate that the resulting amide
of
the diamine, which forms the cationic softener base, is the fatty acid
monoamide
or the diamide or a mixture thereof.
U.S. Patent 5,488,139 describes an opacifier which is a reaction product of an
alkanol amine and a dimerized acid, wherein the diamine (aminoethylethanol
amine) is preferred, in this Patent, the principal reactant with the amine is
a
dimerized acid.
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Despite the clear advantages traditional opacifiers bring to papermaking,
functional limitations on their use related especially to paper sheet strength
and
porosity have been noticed in mill conditions.
A particular category of chemical additives with both funtional and process
applications are enzymes, which are proteins with catalytic properties.
The use of enzymes is ecologically interesting, and such enzymes can generally
be
applied anywere in the paper, paperboard or even pulp production. The
following
examples illustrate some of the present mill or laboratory applications for
enzymes:
~ Xylanases - for prebleaching and bleaching pulps, especially Kraft.
~ Pectinases and xylanases - for debarking.
~ Laccases, proteases - for mechanical pulp refining
~ Cellulases and xylanases - for chemical pulp refining
~ Cellulases - for recycled pulp refining
~ Cellulases - for KAPPA number reduction in Kraft cooking
~ Xylanases - for brightness reversion
~ Cellulases, amylases, xylanases, lipases - for deinking
~ Cellulases - for tissue softness
~ Laccases - for mechanical pulp strength
~ Manganese peroxidases - for chemical pulp strength
~ Cellulases - for chemical fibre liming reduction
~ Laccases - for increased chemical fibre bulk
~ Cellulases and xylanases - for increased chemical fibre flexibility
~ Cellulases - for reduced porosity and increased fibrilation of chemical
fibres
~ Cellulases and amylases - for increased drainage
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~ Esterases - for stickies reduction
~ Amylases, proteases, levan hydrolase - for paper machine cleaning
~ Acetyl esterase, pectinases - for mechanical pulp white water treatments
~ Peroxidases, laccases, catalases - for effluent treatments
~ Pectinases - for cationic demand reduction in peroxide bleached
mechanical pulp
In the prior art, W095/27825 discloses a preparation process for increasing
the
content of inorganic fillers while maintaining or increasing the Scott
internal bond
strength, by addition of a cellulase type enzyme. Increasing the content of
inorganic fillers is known in the art to be needed for particular
applications;
inorganic fillers function as opacifiers.
Increasing the level of inorganic fillers for the majority of specific paper
grades
very often equates into one or more of the following disadvantages:
~ Increased paper machine blades abrasion
~ Increased paper machine press rolls wear
~ Increased paper machine inorganic deposits and breaks
~ Increased chemical costs in papermaking (e.g. when Ti02 is used)
~ Increased printer equipment abrasion
All these reasons justify the use of traditional organic opacifiers rather
than
inorganic filleras as opacifiers.
In the prior art. it was known that increasing the levels of inorganic fillers
favors
opacity increase, but also results in decrease in strength.
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SUMMARY OF THE INVENTION
Surprisingly, while investigating porosity increase enzymatic applications, it
has
now been discovered that some enzymes also improve opacity without the
drawbacks associated with traditional organic opacifiers. The handsheets made
with enzyme treated fibres were often less porous, with increased tensile
strength
as compared with the untreated controls; and were much less porous, and
exhibited much higher tensile strength as compared with the traditional
organic
opacifier treated handsheets.
In this invention, the opacity obtained with enzymes as opacifying agents was
higher or similar to that obtained with traditional organic opacifiers while
porosity
and strength properties were clearly improved.
Although the prior art such as W095/27825 shows that a cellulase can increase
an
internal bond strength of paper, the particular features of the present
invention are
absent from prior art. The prior art contains no showing that enzymes increase
sheet opacity without an increase in the content of opacifying inorganic
fillers.
The enzymes which function as organic opacifying agents may be added during
the course of paper and paperboard manufacturing processes; and can also be
used
in the pulp manufacture stage.
The present invention seeks to provide an agent that adds opacity to paper,
paperboard or pulp to which it is added.
The present invention also seeks to provide an agent for adding to a pulp
slurry of
cellulosic fibers to enhance opacity without adversely affecting other
properties.
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Still further the invention seeks to provide a method of enhancing opacity in
a
paper composition such as paper, paperboard or papermaking pulp.
The present invention also seeks to provide a process of producing paper or
paperboard of enhanced opacity.
The present invention also seeks to provide a papermaking stock, which stock
may
be formed into a paper or paperboard of enhanced opacity.
Still further this invention seeks to provide an opacified paper composition,
for
example a paper, paperboard or papermaking pulp of enhanced opacity.
In particular the present invention seeks to provide a process wherein an
organic
opacifying agent is added to recycled, deinked or virgin pulp of cellulosic
fibers to
form a paper, paperboard or pulp having desirable physical characteristics.
Still further the present invention seeks to provide a process for adding a
composition to pulp slurry of cellulosic fibers in a papermaking process that
results in a paper, paperboard or pulp having enhanced opacity.
The present invention also seeks to provide a paper, paperboard, pulp or pulp
slurry having the desirable characteristic of enhanced opacity.
In accordance with the invention, there is provided in a method of enhancing
opacity in a paper composition, in which an organic opacifying agent is
incorporated in the paper composition, the improvement wherein the organic
opacifying agent comprises an enzyme selected from the group consisting of
hydrolases and oxidoreductases.
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g
In accordance with another aspect of the invention, there is provided an
opacifying
agent for use in enhancing opacity in a paper composition selected from paper,
paperboard and papermaking pulp, comprising an enzyme selected from the group
consisting of hydrolases and oxidoreductases.
In accordance with still another aspect of the invention, there is provided a
papermaking stock comprising: pulp slurry of papermaking fibers and an organic
opacifying agent in an aqueous vehicle; said organic opacifying agent
comprising
an enzyme selected from hydrolases and oxidoreductases.
In accordance with yet another aspect of the invention, there is provided an
opacified paper composition comprising papermaking fibers and an organic
opacifying agent, wherein said organic opacifying agent comprises an enzyme
selected from the group consisting of hydrolases and oxidoreductases.
In accordance with yet another aspect of the invention, there is provided a
process
of producing paper or paperboard of enhanced opacity comprising: i) providing
a
pulp slurry of papermaking fibers, ii) adding an organic opacifying agent to
said
slurry, and iii) forming paper or paperboard from said slurry, wherein said
organic
opacifying agent comprises an enzyme selected from hydrolases and
oxidoreductases.
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DETAILED DESCRIPTION OF THE INVENTION
The invention employs an organic opacifying agent which avoids disadvantages
associated with traditional inorganic opacifying agents while providing
superior
physical properties as compared with prior organic opacifying agents.
The organic opacifying agents of the invention comprise a hydrolase or an
oxidoreductase enzyme. A preferred hydrolase is a cellulose (E.C.3.2.1.4); a
preferred oxidoreductase is laccase (E.C.1.10.3.2).
Hydrolases are enzymes that catalyse the hydrolysis of a chemical bond,
whereby
a molecule is cleaved into two parts by the addition of a molecule of water.
The
catalysed reaction would have the following form:
A-B + HZO ~ A-OH + B-H
The chemical bonds cleaved in this way by hydrolysis include C-O, C-N and C-C
bonds or in the case of organophosphorous hydrolases even P-O, P-F and P-S
bonds.
As shown indirectly in the pulp and paper enzymatic applications example list
hereinbefore, hydrolases are a class of enzymes that benefit from the presence
of
an extremely large group of substrates available for enzymatic action , for
example
cellulose, hemicelluloses and many others, in conjunction with the presence of
water in large quantities in the pulp, paper and paperboard processes.
Cellulases, in particular hydrolyse cellulose, which is an unbranched glucose
polymer composed of 1,4 glucose units linked by 13-1,4-glycosidic bonds, and
is
the main component of pulp, by cleaving the 13-1,4-glycosidic bonds.
Hydrolases
which are cellulolytic enzymes can be classified into three major types:
CA 02523737 2005-10-18
1.0 ENDOGLUCANASES, hydrolyzing randomly the polymeric chain (EC
3.2.1.4)
5 2.0 EXOGLUCANASES, hydrolyzing the ends of the chain:
2.1.1 Cellobiohydrolases, eliberating cellobiose - the glucose dimer (EC
3.2.1.91)
~ Cellobiohydrolases I: hydrolyzing the reducing end
~ Cellobiohydrolases II: hydrolyzing the non-reducing end
10 2.1.2 Glucanhydrolases, eliberating directly glucose
(EC 3.2.1.74)
3.0 13-GLUCOSIDASES or cellobiases, acting on cellobiose or soluble
cellodextrins (EC 3.2.1.21 ).
As shown indirectly in the pulp and paper enzymatic applications example list,
oxidoreductases are a second class of enzymes that benefit from the presence
of an
extremely large group of substrates available for enzymatic action, for
example
lignin, cellulose, hemicelluloses and many others, in the pulp, paper and
paperboard processes.
Oxidoreductases are enzymes that catalyse the transfer of electrons from one
molecule (oxidant or hydrogen donor or electron donor) to another molecule
(reductant or hydrogen acceptor or electron acceptor). The catalyzed reation
would
have the following form:
A +B~A+B
Laccases in particular (EC 1.10.3.2), surprisingly catalyse the oxidation of a
large
number of different substrates, while enzymes in general, for example
cellulases,
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are usually substrate specific. Phenolic lignin units, lignin is an aromatic
heteropolymer of phenyl-propanoid units, many phenolic compounds (diphenols,
polyphenols, different substituted phenols), diamines, aromatic amines,
benzenethiols and some inorganics (e.g. iodine) are oxidised directly with
molecular oxygen as final electron acceptor through laccase action, the oxygen
being reduced to water.
Besides the presence of molecular oxygen, laccases may require organic
mediators
which are sometimes already present in the pulp slurry.
Suitable mediators, by way of example, are 2-2'azinobis(3-ethylbenzthiazoline-
6-
sulfonate); ABTS 1-hydroxybenzotriazole; HBT N-acetyl-N-
phenylhydroxylamine or NHA violuric acid or VIO N-hydroxybenzotriazole or
NHB methyl 3,5-dimethoxy-4-hydroxybenzoate; methyl syringate potassium
octacyanomolybtate; 1-phenyl-3-methyl-pyrazolone sodium; 1-phenyl-3methyl-4-
methylamino-pyrazolone-5-N(4)-methanesulfonate; PPNa 1-(3'sufophenyl)-3-
methylpyrazolone-5); and SPP N-hydroxyphthalimide as well as numerous
phenoxazines and phenotiazines.
The laccase active site contains four copper atoms. In a reported mechanism,
the
separate type 1 copper atom extracts one electron from the substrate, while
the
other copper atoms (one type 2 and two type 3) grouped in a trinuclear cluster
receive the electron through presumably a conserved Hys - Cys - His
tripeptide.
Once the complete reduction in the trinuclear center takes place it is
followed by
the molecular oxygen reduction.
The organic opacifying agent of this invention is usually added to bleached
wood
pulp or recycled paper pulp.
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The organic opacifying agent of this invention can be added alone or in
conjunction with sizing agents, brighteners and other opacifying agents or any
other functional or process additives.
The organic opacifying agent of this invention can be added to any pulp
slurry,
deinked or recycled pulp.
The amount of the opacifying agent and the other components added to the pulp
slurry depends on the type of pulp slurry to which the opacying agent is
added.
The opacifying agent of this invention provides an increase in opacity to the
paper,
paperboard or pulp and provides an improved strength and porosity.
The opacifying agent may be employed in conjunction with a surfactant and
stabilizing agents
Even though the opacying agent can be applied as a powder, typically it is
dispersed in water for addition to the pulp slurry and typically is added in
an
amount of 0.00002% to 2%, preferably 0.0002% to 0.2%, catalytic protein by
weight, based on the oven dry weight of the pulp fibers.
The dispersion in water typically contains 0.1 to 30%, and preferably about 1-
10%, by weight of the catalytic protein.
The opacifying agent of the invention is more efficient and more effective
even at
lower concentration than traditional organic opacifying agents.
The opacifying agent of the invention provides improved opacity to the treated
paper, paperboard or pulp.
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A particular advantage of the present invention is that for a given amount of
inorganic filler, if present, in the paper, paperboard or pulp, which filler
may or
may not have opacifying properties, the opacity is enhanced by the organic,
enzymatic opacifying agent. More especially, it is not necessary to use an
inorganic opacifying agent and it is not necessary to increase the content of
an
inorganic filler having opacifying properties in order to increase the
opacity, and
which increase in content would result in loss of strength. The organic,
enzymatic
opacifying agent of the invention not only enhances the opacity but also
increases
the strength and lowers the porosity.
An inorganic filler is not required in order to provide opacity when employing
the
organic opacity agent of the invention; and the invention contemplates paper
compositions containing the opacifying agent of the invention and being free
of
inorganic filler, although inorganic fillers may be included in the paper
composition for the traditional purpose of reducing the pulp content, without
their
necessity to provide an opacifying function.
The invention is further illustrated by reference to the Examples.
EXAMPLES
Example 1
Laboratory opacity, brightness, porosity and tensile strength testing were
performed with the following materials and methods:
Pulp preparation:
Water deionized at pH 7.0
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Furnish: 400g a.d. pulp: 10% deinked market pulp (40g), 25% Softwood Kraft
(100g a.d.), 65% Hardwood Kraft (260g a.d.).
Additives:
Traditional organic opacifier (amide of fatty acid and diamine), Trizym DEO
(trademark for a cellulase of Tri-Tex), PCC (without dispersant), Ti02
(anatase),
anionic PAM retention aid
Apparatus for pulp preparation:
Beater with controlled bedplate (Pile Valley Iron Works)
British disintegrator
Canadian standard freeness tester
150 microns mesh
Hotplate (Termolyne Cimarec 2TM)
pH meter (VWR scientific model 8000)
Thermometer (Fisherbrand )
Caframo stirrer RZRSOT"~
1000 ml beaker
In all trials (control / amide of fatty acid and diamine / cellulase) the pulp
treatments were made as described below:
1) In a first stage refining was performed for the entire 400 g a.d. of pulp
according to TAPPI T 200 om-85 to a freeness of 300 ml CSF. Following the
refining, pulp consistency was adjusted to 3% by filtration through a 150
micron mesh.
2) In the second stage 30g a.d./trial of fibre (1000g pulp) were heated and
maintained at 55°C for 20 minutes with opacifier additions or with no
opacifier
additions (control) in a 1000m1 beaker on the hotplate, while stirring at 300
CA 02523737 2005-10-18
rpm. The opacifier additions were made at 0.2% as is / a.d. fibre for Trizym
DEO (trademark for a cellulase of Tri-Tex) and at 0.2% dry / a.d. fibre for
the
traditional organic opacifier (amide of fatty acid and diamine)
3) In the third stage 15% PCC (4.5g dry) and 15% Ti02 (4.5g dry) addition was
S followed by 10 minutes of stirring while maintaining 55°C pulp
temperature.
4) In the fourth stage the heating was stopped and the pulp was diluted to 1 %
with
the addition of 2000g deionized room temperature water, followed by 0.1
(0.03g dry) anionic PAM addition and 2 minutes stirring at 200 rpm.
10 Handsheet preparation for optical testing was made with a slight
modification of
TAPPI T 218 om-83 without a dispersion stage, with conditioning (without
preconditioning) according to TAPPI T 402 om-88 for 5 hours at 23°C and
51
RH. The modification aimed at improved monitoring of the effect of fines and
white water recirculation on opacity, concerned reusing three times the white
15 water resulting from sheet formation and retaining for testing only each
fourth
sheet.
Handsheet preparation for physical testing was made with a slight modification
of
TAPPI T 205 om-83, with conditioning (without preconditioning) according to
TAPPI T 402 om-88 for 5 hours at 23°C and 51% RH. The second
modification
aimed at improved monitoring of the effect of fines and white water
recirculation
on porosity, concerned reusing three times the white water resulting from
sheet
formation and retaining for testing only each fourth sheet.
Handsheet printing opacity (ISO standard 2471) and ISO brightness testing were
made in the conditioning temperature and humidity conditions after 5 hours
from
the handsheet preparation on a Technibrite Micro TB-1 CT"~.
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Handsheet tensile strength (TAPPI T 220 om-88 and TAPPI T 494 om-88) and the
air resistance of paper (TAPPI T 460 om-88) were tested in the conditioning
temperature and humidity conditions after 5 hours from the handsheet
preparation
with a MC TEC vertical tensile tester and a UEC - 1012 - A densometer tester.
Trial ISO ISO Densometer Tensile
nr. Brightness Opacity sec / 100m1Strength
air kN/m
1 Control 86.50 80.69 63 4.8
2 amide of 86.88 81.58 55 4.4
fatty acid
and diamine
cellulase ~ 86.91 82.71 121 ~ 5.4
~ ~
Example 2
Laboratory opacity, brightness, porosity and tensile strength testing were
performed with the following materials and methods:
Pulp preparation:
Water deionized at pH 7.0
Furnish: 400g a.d. pulp: 10% deinked market pulp (40g), 10% Aspen BCTMP
(40g) 25% Softwood Kraft (100g a.d.), 55% Hardwood Kraft (220g a.d.).
Additives:
Traditional organic opacifier (amide of fatty acid and diamine), Trizym DLC
(trademark for a laccase of Tri-Tex), PCC (without dispersant), Ti02
(anatase),
anionic PAM retention aid
Apparatus for pulp preparation:
Beater with controlled bedplate (Pile Valley Iron Works)
British disintegrator
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Canadian standard freeness tester
150 microns mesh
Hotplate (Termolyne Cimarec 2T"")
pH meter (VWR scientific model 8000)
Thermometer (Fisherbrand )
Caframo stirrer RZRSOTM
1000 ml beaker
In all trials (control / amide of fatty acid and diamine / laccase) the pulp
treatments
were made as described below:
5) In a first stage refining was performed for the entire 400 g a.d. of pulp
according to TAPPI T 200 om-85 to a freeness of 300 ml CSF. Following the
refining, pulp consistency was adjusted to 3% by filtration through a 150
micron mesh.
6) In the second stage 30g a.d./trial of fibre (1000g pulp) were heated and
maintained at 55°C for 20 minutes with opacifier additions or with no
opacifier
additions (control) in a 1000m1 beaker on the hotplate, while stirring at 300
rpm. The opacifier additions were made at 0.2% as is / a.d. fibre for Trizym
DLC (trademark for a laccase of Tri-Tex) and at 0.2% dry / a.d. fibre for the
traditional organic opacifier (amide of fatty acid and diamine)
7) In the third stage 15% PCC (4.5g dry) and 15% Ti02 (4.5g dry) addition was
followed by 10 minutes of stirring while maintaining 55°C pulp
temperature.
8) In the fourth stage the heating was stopped and the pulp was diluted to 1 %
with
the addition of 2000g deionized room temperature water, followed by 0.1
(0.03g dry) anionic PAM addition and 2 minutes stirring at 200 rpm.
Handsheet preparation for optical testing was made with a slight modification
of
TAPPI T 218 om-83 without a dispersion stage, with conditioning (without
preconditioning) according to TAPPI T 402 om-88 for 5 hours at 23°C and
51
RH. The modification aimed at improved monitoring of the effect of fines and
CA 02523737 2005-10-18
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white water recirculation on opacity, concerned reusing three times the white
water resulting from sheet formation and retaining for testing only each
fourth
sheet.
Handsheet preparation for physical testing was made with a slight modification
of
TAPPI T 205 om-83, with conditioning (without preconditioning) according to
TAPPI T 402 om-88 for 5 hours at 23°C and 51 % RH. The second
modification
aimed at improved monitoring of the effect of fines and white water
recirculation
on porosity, concerned reusing three times the white water resulting from
sheet
formation and retaining for testing only each fourth sheet.
Handsheet printing opacity (ISO standard 2471) and ISO brightness testing were
made in the conditioning temperature and humidity conditions after 5 hours
from
the handsheet preparation on a Technibrite Micro TB-1CT""
Handsheet tensile strength (TAPPI T 220 om-88 and TAPPI T 494 om-88) and the
air resistance of paper (TAPPI T 460 om-88) were tested in the conditioning
temperature and humidity conditions after 5 hours from the handsheet
preparation
with a MC TEC vertical tensile tester and a UEC -1 O l 2 - A densometer
tester.
Trial ISO ISO DensometerTensile
nr. Brightness Opacity sec / 100m1Strength
air kN/m
1 Control 86.11 80.51 52 4.3
2 amide of 86.48 81.38 45 4.0
fatty acid
and diamine
3 laccase 86.53 81.59 57 5.1
